Heretofore, several apparatus for effecting an oxidizing reaction of liquid or gaseous fuel on a solid oxidizing catalyst have been proposed, for example, an apparatus as shown in FIG. 1 (Catalyst, Vol. 29, No. 4, 313, 1987).
In FIG. 1, numeral 101 denotes a fuel pipe, numeral 102 ejection ports, numeral 103 an insulator layer, numeral 104 an electric heater, numeral 105 a catalyst layer, and numeral 106 a cover. Fuel is supplied through the ejecting ports 102 formed in the fuel tube 101 in a distributed manner, and passed through the porous insulator layer 103 to the catalyst layer 105 which is preheated by the electric heater 104. On the other hand, air is supplied from the underside of the cover 106 under the function of convection. Near the surface of the catalyst layer 105, the fuel and the air are mixed with each other by diffusion, and a catalytic burning is effected on the fibered porous catalyst layer 105.
The catalytic burning apparatus of this type, however, has problems as follows. Firstly, it is required to heat the catalyst layer 105 to a temperature at which the catalytic reaction starts, and it takes a long time to heat the catalyst layer to the predetermined temperature by the electric heater 104, unless a heater of a great capacity is used. Secondly, since the catalyst layer 105, from the surface of which the heat is radiated forwards, is only covered in a halfly exposed manner by the cover 106 made of such as a porous metal, there is a fear that the burning is interrupted by a gust or a water spray, frequently causing an imperfect combustion and producing an offensive smell and a harmfull carbon monoxide. Thirdly, when the apparatus is used for a long time and the activity of the catalyst layer is deteriorated, there occurs a fear that the imperfectly burned fuel flows out, and an offensive smell and a great amount of harmful carbon monoxide are continuously produced due to the imperfect combustion, because there is provided no detecting means for detecting the deterioration of the catalyst layer. Fourthly, in the case where the fuel is burned in a closed space such as in a room, the burning is not stopped as far as the temperature of the catalyst layer is maintained in a predetermined range, even when the oxygen density has been decreased to a level having an adverse influence on the human health, thereby causing a continuation of the oxygen starvation and the imperfect combustion.